Signal wave form indicating system



May. 26, 1942. A. v. LOUGHREN I I SIGNAL WAVE FORM INDICA'TING SYSTEM Filed Nov. 26, 1940 3 Sheets-Sheet 2 w HM; b Fig.6.

INVENTOR ARTHUR V. LOUGHREN BY ATTORNEY Patented May 26, 1942 T OFFICE SIGNAL wave roam mnioarmo SYSTEM Arthur v. Loughren, Great Neck, N. to 'Hazeltlne Corporation,

. Delaware Y., asslgnor a corporation of Application November 26, 1940, Serial No. 367,248

24 Claims.

The present invention relates to an improved wave form indicating system and, particularly, to a system for visually indicating at least the synchronizing-signal portion of the wave form of a television signal.

The conventional television signal of the present day transmits two forms of information, each of equal importance to the satisfactory reproduction of the television image. One form of information corresponds to the details of the transmitted image itself and the other, the signal' components assuring the proper synchronization of the operations ofthe transmitting and receiving apparatus. The proper composition of a television signal is highly important in order that the several types of information conveyed by the signal may be separated at the receiver and individually supplied to its several units to control the operational each. The composition of the television signal can be ascertained by inspection of its wave form.

There has heretofore been no simple system available by which an inspection of the wave form of a television signal could be'made in a simple and direct manner. Particularly is this true of the synchronizing information comprising the line-synchronizing and field-synchronizing components of the signal, usually in the form of line-frequency and field-frequency synchronizing pulses, the latter consisting of pulses of relatively long duration preceded and followed by equalizing pulses which are of twice the frequency of the line-synchronizing pulses and onehalf their duration; The line-synchronizing pulses are positioned in the television signal at I-' points corresponding to the intervals between successive lines of the television image, commonly known as the line-retrace intervals, while the field-synchronizing and equalizing pulses are positionedat points corresponding to the intervals between successive fields or series of lines forming an image, known as the field-retrace intervals. The particular positioning of the linesynchronizing pulses, the field-synchronizing pulses, and the equalizing pulses is important not only in the relation to the start and finish of the intervals in which each occurs. but also in regard to the relative phase of the field-synchronizing and equalizing pulses considered with respect to each other and to tho line-synchronizing pulses.

, It is further important that the several types of synchronizing pulses have predetermined individual durations.

In examining the wave form of the synchronizing-signal componentsof a television signal. it has heretofore been necessary to examine successively, by the use of an oscilloscope, a large number of individual sections or portions of the television signal each corresponding to one line or a few lines of the transmitted image. These curately the numerous examinations obviously necessitate a large number of individual adjustments of the oscilloscope apparatus, and this method of wave form investigation is tween one or more of the several independent investigations. Furthermoresuch successive investigations often do not show'completely or acphase relations between the several synchronizing-signal components. Consequently, it is highly desirable that there be provided an accurate single visual indication of the wave form of all synchronizing-signal components of the television signal in tion of the signal may be curately determined.

It is an object of the present invention, therefore, to provide a new and improved system for visually indicating at least a portion of the wave form of a television signal and one which avoids one or' more of the above-mentioned disadvantages and limitations of the prior art wave form indicating systems.

It is an additional object of the invention to provide an indicating system which furnishes a single visual indication of the entire wave form of a television signal and particularly of the portions thereof which are essential to accurate synchronization between the transmitting and the receiving television apparatus.

easily, quickly, and ac- It is a further object of the invention to pro- I vide an indicating system which furnishes a single visual indication of the wave form ofall of the synchronizing-signal components of the television signal and particularly furnishes an indication of the relative phase relationships between the several synchronizirig-signal components.

In accordancewith the present invention, a system for visually indicating at least a portion of the wave form of a television signal comprises a cathode-ray tube having an input circuit adapted to have applied thereto a television signal to modulate the ray of the tube, the applied signal including synchronizing-signal components. The system includes means for periodically deflecting the ray of the tube in each of two directions normal to each other, means for controlling the deflecting means to maintain the deflections in synchronization with the synchronizing-signal components of the applied signal, and means for maintaining a predetermined phase displacement between'one or both of the ray deflections and the corresponding synchrofrequently not satisfactory since changes may occur in the wave form beorder that the composi- Fig. 6 illustrates a 2 mined phase-displaced synchronism with the synchronizing-signal components of the applied television signal.

For a better understanding of the invention,

In the accompanying drawings, Fig. l is a circuit diagram, partially schematic, of a complete television carrier-signal receiver including a system embodying the invention for visually indicating at least a portion of the wave form of a receivedtelevision signal; Fig. 2 illustrates a visual pattern produced by the wave form indicating system of the Fig. 1 arangement and indicating the wave form of the synchronizingsignal components of a television signal having proper composition; Fig. 3 is a graph of the wave form of a portion of a conventional negatively-modulated television signal and is used in explaining the manner of interpreting the pattern produced by the wave form indicating system; Fig. 4 is a graph of the wave form of a portion of a television signal and shows periodic time-reference oscillations superimposed on the television signal; Fig. 5 represents schematically a television transmitting apparatus having associated therewith as a monitoring device the wave form indicating system of the invention;

dicating system to indicate the wave form of a television signal having improper composition; and Fig. '1 is a partial circuit diagram of a modified form of the'field-sy'nchronizing portion of the indicating system of the invention.

Referring now more particularly to- Fig. 1, there is represented schematically a television carrier-signal receiver including a wave form indicating system embodying the present invention in a preferred form. In general, the receiver includes a radio-frequency amplifier ll having its input circuit connected to an antenna system II, II and having its output circuit connected to an oscillator-modulator I3. Connected in cascade with the oscillator-modulator is, in the order named, are an intermediatefrequency amplifier ll of one. or more stages, a detector and A. V. C. supply II, and a videofrequency amplifier it. The output circuit of the video-frequency amplifier I. is coupled by way of an input circuit to the ray-control or modulation-control electrode of a cathode-ray tube It provided in a wave form indicating system ll, more fully describedhereinafter. The output circuit of the detector of unit II also is coupled to a synchronizing-signal separator ll included in unit II. The A. V. C. supply of unit It is connected through the conductor designated as A. V. C. to the input circuits of one or more of the tubes of units II, It, and H in a' conventional manner.

It will be understood that the various units Just described may, with the exception of the wave form indicating system it, be a conventional construction and operation, the details of which are well known in the art, rendering detailed description thereof unnecesary. Considering briefiy the operation of this portion of the receiver and of the wave form indicating system II as a whole, and neglecting for the moment the detailed operation of the indicating system, presently to be described, a television modulated-carrier signal is received and ampattern produced by the in-' received signal intensities.

generators 22 and 23 to app y windings. The indicating system ll plified by the radio-frequency amplifier ii, converted to an intermediate-frequency carrier sigml in the oscillator-modulator It. amplified in the intermediate-frequency amplifier N, and detected by the detector of unit ii to derive the video and synchronizing-signal modulation components thereof. The modulation components are amplified by the video-frequency amplifier IO and applied to the input circuit of the cathode-ray tube it. The cathode-ray beam of tube ll periodically is deflected in two directions normal to each other, but these deflections are maintained in predetermined phase-displaced synchronism, in a manner presently to be described in greater detail, with the synchronizing-signal components of the television signal applied to the synchronizing-signal separator l1 and to the cathode-ray tube II. There is consequently formed on the screen of tube it a pattern representative of the synchronising-signal components, since they are displaced in phase.with respect to the retrace intervals of the signal input to the cathode-ray tube ll, during which the scanning ray is normally suppressed.

The automatic amplification control or A. V. C. bias derived from the A. is efiective to control the amplification of one or more of the units II, it, and II to maintain the signal input to the detector of unit I! within a relatively narrow range for a wide range of Referring now more particularly to the wave form indicating system It embodying the present invention in a preferred form, the cathode-ray tube II has an input circuit 2|, 1| coupled across a cathode resistor O which is common to the output circuits of a video-frequency amplifier I and a harmonic-frequency amplifier I. The input circuit of amplifier I is coupled to the output circuit of the video-frequency amplifier ll and includes a network 0 which inserts a direct current component of the video-frequency signal at the grid of amplifier U using the synchronizing signai pulse tips as its reference level. Thus, the raycontrol electrode of tube It is adapted to have applied thereto by way of the input circuit 20, 2| the television modulation-signal output of videofrequency amplifier I. to modulate the ray of the tube and the television signal includes synchronizing-signal components comprising linefrequency and field-frequency synchronizing pulses. In order to deflect the ray of tube It periodically and with substantially constant velocity in each of two directions normal to each other to produce a series of lines and a series of fields, there is provided defiecting means comprising a line-scanning generator 22 and a fieldscanning generator 23. the outputs of which are respectively coupled to the line-deflecting and field-deflecting elements of tube It, which may be deflecting plates, as indicated, or deflecting includes also means responsive to the synchronizingsignal components of the television signal for controlling the generators 22 and 23 to maintain the cathode-ray deflections in synchronism with the synchronizing-signal components of the applied television signal. This means comprises the synchronizing-signal separator l1 having an input circuit coupled to the output circuit of the detector of unit II and having a pair of output circuits individually coupled to the scanning to these generators v. C. supply of unit II f placements between the cathode-ray deflections and corresponding ones 01' the synchronizingsignal components of the television signal applied to the tube IQ, of such value as to remove the synchronizing-signal components from the retrace intervals of the cathode-ray deflections,

comprising two signal delay circuits 24 and 25 which are individually included in the means for controlling the ray deflecting means. Specifically, the delay circuits 24 and 25 are included in the coupling circuits betwen the synchronizingsignal separator I! and the respective scanning generators 22 and 23. The network 24 com prises a low-pass filter consisting of a plurality of series-inductance arms 26, 26, 23, a plurality of shunt-capacitance arms 21, 21, 21, and a terminating impedance 28 having a value equal to the image impedance of the network 24. The constants of network 24 are so proportioned that the network has a phase delay equal to a predetermined portion of the period of the line-synchronizing pulses.

The signal delay circuit 25 comprises a pair of vacuum-tube triodes 30 and 3| having input and output circuits cross-connected to form a multivibrator type of oscillation generator and means responsive to the field-synchronizing pulses for controlling the frequency of the generated oscillations. To this end, the input circuit of triode 33 is additionally coupled to the synchronizing-signal separator ii to have applied thereto the fleld-trequency synchronizing pulses of the television signal. The output circuit of the triode 3i is coupled to the synchronizing circuit of the field-scanning generator 23 which circuit comprises means responsive to the waveform of the generated oscillations for controlling the ray-deflecting means to maintain the deflection fields in predetermined phase-displaced synchronism with respect to the fieldsynchronizing pulses. Circuit 25 generates oscillations having a substantially rectangularpulse wave form and there is provided means for controlling the duration of the pulses of the generated wave comprising an adjustable resistor 32 coupled 'between the grid and cathode elements of the triode 3|. Vacuum tubes 30 and 3| are energized from a source of cated as +3.

The indicating system l8 also includes 'means for developing a periodic potential having a period equal to a predetermined fraction of the time required for one deflection of the ray across the screen of the tube and for additionally modulating the ray of tube l9 therewith to provide time-reference indicia on the screen of the cathode-ray tube. This means comprises a harmonic generator 33 having an input circuit coupled to the synchronizing-signal separator H t have applied thereto the line-synchronizing pulses of the television signal. The output-circuit of generator 33 is coupled through means, the harmonic-frequency amplifier 1, to the input circuit 20, 2| of tube l9. This generator generates oscillations effectively of pulse-wave form having a frequency equal to a predetermined multiple or harmonic of the frequency of the line-synchronizing pulses. The input circuit of amplifier 7 includes a network which so biases the grid of amplifier 1 as to maintain the peak amplitude of the output of the harmonic oscillaspace current indi-j tions of generator 33 at a predetermined level at the grid 01' amplifier 1.

The indicating system it further includes means for so adjusting the level or the television signal as applied to the input circuit of tube l3 that either all or only predetermined portions of the amplitude range of the synchronizing-signal on the screen of the cathode-ray tube;

components are reproduced bythe tube, or the level may be so adjusted that, in addition, all or predetermined portions of the television image are reproduced. This means comprises an ad- Justable contact a on the supply source for the several electrodes of tube l3, indicated as battery B,.whereby the bias of the input electrodes of tube i9 is so adjusted that any selected level of the applied television signal'is effective to extinguish the cathode-ray beam.

In considering the operation of the circuit just described, it will be assumed that there is applied from the video-frequency amplifier IE to the input circuit of cathode-ray tube is a television signal having such polarity that the line-frequency and field-frequency synchronizing pulses of the television signal are reproduced as white that is, the polarity of the applied television signal is such that the synchronizing-signal components increase the beam current of the cathode-ray tube, which is opposite the conventional television practice. The line-synchronizing pulses of the television signal are separated from the image-signal component and the field-synchronizing pulses by the synchronizing-signal separator l1 and are applied both to the harmonic generator 33 and to the input of the delay network 24. The harmonic generator 33 is of the type which generates oscillations having a frequency equal to that ofthe line-synchronizing pulses but having a wave form rich in harmonics.

A desired harmonic, for example, the onehundredth harmonic, is selected in the output of the harmonic generator and is applied through the harmonic-frequency amplifier I to the input circuit of. cathode-ray tube is is reproduced on the screen of tube is as a series of, bright dashes spaced across the cathode-ray tube screen and these dashes are in alignment and form, in a manner to be hereinafter more fully described, a series of bright lines normal to the line-scanning direction. These lines are useful as an accurate means of measuring the durations and relative phase relationships of the synchronizing-signal components, the wave forms of which are indicated by the pattern produced on the screen of tube IS. The choice 7 of any particular harmonic is a matter of convenience, the one-hundredth harmonic having the particular advantage that it permits reading time intervals directly in percentage of the line-synchronizing pulse period. The provision of time-reference lines in this manner is especially useful when the line deflections of the cathode ray of tube l9 do not have uniform velocity throughout the entire period of the line deflection. The use of a common cathode resistor 9 for amplifiers 1 and 3 permits amplifier 8 to bias amplifier 1 to cutofl' at a predetermined level on the television signal. This predetermined level may be chosen by suitably proportioning the biases of amplifiers 1 and 8 to be the level corresponding to black in the television so that each line sponds to positive pulses only. After a line-synchronizing pulses of the television signal applied to tube l9, the magnitude of the phase displacement equalling the phase delay of the network. These derived synchronizing pulses are applied to a synchronizing means which may from the conventional reproduction, in which these pulses occur during the retrace interval of the scanning beam and in which the signal level terminology by which the positive during such intervals is such that the blanking pulses block out the scanning beam to prevent reproduction of the synchronizing pulses.

The field-synchronizing pulses from the synchronizing-signal separator II are applied to oscillator 25 to maintain the generated oscillations in synchronism with the field-synchronizing pulses. Assuming triode 30 to be conducting, at a'time just prior to the time when a pulse is to be applied to its grid from triode II, a synchronizing pulse is applied negatively thereto from the synchronizing-signal separator l1 which triggers the multivibrator, biasing triode l. to cutoff. The potential of the anode of triode l! thereupon rises to value +18 and supplies a positive pulse to the grid of the then inert triode 3|. Tricde 3| immediately becomes conductive, whereby its anode potential becomes less positive, supplying a negative pulse to field-scanning generator 23 which is not affected since it repredetzrmined interval, determined by the time constant of the grid circuit of triode 3!, the charge leaks on the grid and triggers triode 8|, biasing it to cutoff, whereupon its anode potential rises to value +3 and supplies a positive pulse to drive field-scanning generator 23 and to trigger triode so, rendering it conductive. Hence, it will be seen that the field-synchronizing arrangement includes means responsive to the field-synchronizing pulses multivibrator at a predetermined point on half cycles of one polarity of the generated oscillations and means for synchronizing the fieldirequency oscillator at a predetermined point on half cycles of opposite polarity of the generated osci'lations. The synchronization of the fieldscanning generator 23 is thus displaced in phase with respect to the field-synchronizing pulses applied to the triode II. The resultant fieldscanning deflections of the cathode-ray beam 0! tube is, which are produced by the oscillations generated by generator 23, are consequently displaced in phase with respect to the field-synchronizing pulses of the television signal applied to'the brilliancy-control electrode 0! the cathode-ray tube is. As a result, the equalizing pulses and the field-synchronizing pulses of the television signal are reproduced on the screen of tube l9 well within the picture area thereof as distinguished from the conventional reproduction, in which these pulses occur during the retrace interval and are blocked-out from the reproduced television image.

The adjustable grid resistor 32 of oscillator 25 controls the relative durations of the positive and negative halt-cycles oi the generated oscili or synchronizing the -used,andasusedin signal having a wave lations. Since the grid resistor 32 maybe so adjusted that the positive and negative halt-cycles oi the generated oscillations have unequal durations, the expression halt-cycles" as here the claims, is not strictly for want of more accurate and negative loops of the generated oscillations may be designated in terms 0! their "polarity." Adjustment of the value of grid resistor 32 thus eiiectively varies the magnitude oi! the phase shift between the field-scanning deflections c! the ray of tube II and the field-synchronizing pulses of the television signal applied to the input electrodes of cathode-ray tube I! and consequently varies the region within the picture area at which the cqualizing pulses and field-synchronizing pulses are reproduced.

Fig. 2 illustrates the pattern produced on the screen of the cathode-ray tube II by a television form properly composed in accordance with the present standards approved by the Radio Manufacturers Association. As an aid in interpreting the pattern of this figure, reference is made to Fig. 8 which graphically illustrates the wave form of a television signal having proper composition. The television signal comprises line-synchronizing pulses b occurring during the interval between successive lines c o! the image-signal component, the latter being here represented as an im e signal corresponding to a uniformly white background of intensity W. Each line period has a duration t and each line-retrace interval has a duration accurate but is used -t1. To provide accurate synchronization, the I leading edge of each line-synchronizing pulse occurs a time interval t: after the initiation of each line-retrace interval and has a duration t1. Similarly, the field-retrace interval occupies a time h during which interval a series of equalizing pulses d precede and follow a field-synchronizing pulse e of relatively long duration and periodically serrated at I to form a series of broad pulses e, the serration of pulse e being provided to assist in maintaining line-frequency synchronization. The equalizing pulses have a duration ta approximately one-half the lines synchronizing pulse duration t: and a period is one-half the period t o! the line-synchronizing pulses. The duration of each of the broad pulses e' of the field-synchronizing pulse e is t1 and the duration of each serration I is is. The duration of the field-synchronizing, pulse e is tn.

The pattern illustrated in Fig. 2 may be termed a pulse-cross pattern since the synchronizing-signal components of the television signal produce a white cross within the picture area. This white cross is superimposed upon a broader grey cross which is produced by the normal black -level B. Fig. 3, of the television signal during the line-retrace and field-retrace intervals. To derive the pattern of Fig. 2, the adjustable contact a of battery B is set to bias thecathode-ray tube It to cutoi! at a level W1 of the television signal representing a dark grey shade level, a value or bias which suppresses the video-signal component of the signal. The line-retrace or blanking interval h of the television signal is indicated on this pattern by the width h of the wide vertical gre bar lr oi the cross. The line-synchronizing pulses b produce the narrower vertical white bar 11 and their duration t; is indicated by its width 1:. The interval t: of Fig. 3 is indicated by the width t: of the narrow vertical grey strip a which lies to the left of the white vertical bar. The equalizing pulses d produce the rectangular white areas d, d which lie immediately above and below the horizontal white bar of the cross, and theirduration is indicated by the width is of these areas. The broad pulses e of the field-synchronizing pulse e produce the horizontal white bar e of the cross, and their duration is indicated by the length i? of the left-hand portion of the horizontal white bar. The interval of each serration f of the field-synchronizing pulse e is indicated by the length is of the gap which occurs in the horizontal white bar e'. The field-retrace intervals t4 produce the horizontal grey bar fr of the cross, and their duration is indicated in Fig, 2 by the width it of the wide horizontal gre bar. The duration of the field-synchronizing pulse e is indicated by the width is of the narrow horizontal white bar e of the cross pattern. The widths in and k of the white rectangles d, d which lie respectively above and below the horizontal white bar e is a measure of equalizing pulses d while the width m of the horizontal grey bar fr below the lower white rectangle d is a measure of the number of linesynchronizing pulses b which follow the equalizing pulses d.

It may be noted that the width t4 of the horizontal grey bar may be increased appreciably over that shown in Fig. 2 by suitably increasing the amplitude of the oscillations generated by the field-scanning generator 23. This has the advantage that the several intervals m, k, h, it, and t9, and the number of pulses occurring during these intervals, may be more accurately established by counting the number of narrow white lines which form the horizontal grey bar fr and broader white lines which form the horizontal white bar e, the increased width of the horizontal grey bar making for greater ease in distinguishing the narrow and broader white lines.from one another. The pattern of Fig. 2 was prepared in this manner while the pattern of Fig. 6, presently to be considered, was not.

Fig. 4 is a graph representing the wave form of two lines only of the television signal with the harmonic oscillations n of the harmonic generator 33 superimposed thereon. The peak amplitude of the harmonic oscillations n are stabilized at the black level of the television signal by the interrelated operation of amplifiers 1 and B and break up each line into a series of dashes, the dashes being aligned to produce the vertical white lines 11. on the pattern of Fig. 2. These lines are useful as an accurate means of measuring the durations and relative phase relationships of the synchronizing-signal components the wave forms of which are indicated by the pattern of Fig. 2.

An inspection of the pattern of Fig. 2 indicates that the wave form of the television signal which produced this pattern conforms to the abovementioned standards of the Radio Manufacturers Association. The leading edges of the linesynchronizing pulses, the equalizing pulses, and the field-synchronizing pulses are properly timed, as indicated by the unbroken straight lefthand edge of the vertical white bar b of the cross pattern. The equalizing pulses have a duration t5 one-half that of ta of the line-synchronizing pulses, The width ii of the vertical grey strip 7 of the vertical grey bar Zr indicates that the line-synchronizing pulses b occur approximately /100 of the line period after the initiation of each line-retrace interval. A close inof the number 5 spection of the horizontal grey bar fr shows that this bar is formed of six narrow white lines above and nineteen narrow white lines below the white bar e. The white lines above the horizontal white bar e indicate that there are twelve equalizing pulses in all preceding the field-synsynchronizing pulses'in each of the two interlaced fields following the last group of equalizing pulses. An inspection or the horizontal white bar e shows that this bar is formed of six broader white lines which are broken by the gap 1 to form twelve line sections, thereby indicating that there are six broad pulses e in each fieldsynchronizing pulse e of the interlaced fields.

In the foregoing described operation of the invention, it was stated that the video-signal component of the television signal is suppressed by so adjusting the adjustable contact a of battery B that tube I9 is biased to cutofl at the to be described.

- system 31, 38. A timer lib level W1, Fig. 3, of the television signal.

.will be evident that the contact a may also be so adjusted that the entire television signal including its video-signal component is reproduced on the screen of tube l9, as in Fig-6 presently The synchronizing-signal components of the television signal may alone be reproduced, as a white cross on the black background, by adjustment oi the contact a to bias the input electrodes 01' tube I9 to cutofi at the level B, Fig. 3, of the television signal. By applying the television signal with conventional polarity to the input electrodes of tube l9, which polarity is opposite to that assumed in the foregoing described operation of the invention, th synchronizing-signal components may be reproduced as a black cross within the picture area by so adjusting the contact a that tube I 9 is biased to cutoff at a predetermined amplitude on the synchronizing-signal pulses.

Fig. 5 represents schematically a use of the wave form indicating system of the invention in monitoring the wave form of the television signal at the television transmitter. The transmitter includes an image-signal and scanning generator unit 34 comprising a suitable videofrequency amplifier. Connected in cascade to the output of the image-signal generator 34, in the order named, are a modulator amplifler 35, a carrier-signal amplifier 36, and an antenna 39 is energized from a GO-cycle alternating current power supply 40, 40 and generates periodic pulse potentials of suitable wave forms having frequencies of cycles, 13,230 cycles, and 26,460 cycles. These potentials are applied to the image-signal generator 34 through conductors 41-45, inclusive,

to control its operation. Line-synchronizing and field-synchronizing pulses generated by timer 39 are also applied through conductors 46 and 41 to the modulator-amplifier 35 where they are combined with the image signal to provide a composite television signal which is used to modulate a carrier signal generated therein which is applied to the carrier-signal amplifier 36. The output of the modulator-amplifier 35 is coupled by conductors 48 and 49 to the, input circuit of the cathode-ray tube I 9 01' the wave circuits :4 and as,

' bines the image signal with iorm indicatin sy tem ll. Synchronizin pulses" having irequencies sive,to indicatingsystemltsuchasthep base-dell! veimoitheunitil Just described m y. wave iorm-indicating system it, be of a conventional construction and operation the details 01 which are well known in the art, rendering iurther detailed description thereoi unnecessary.

the operation oi the trans- Considering brien and referring to the above mitter as a whole, detailed description iorm indicating system ll, an image signal is developed by the generator it and is applied to the modulator-amplifier ii. The latter comthe line-synchroniz- Flg. 6 illustrates a pulse-cross pattern produced by a television signal improperly comdue to an improper adjustment oi the transmitting arrangement of Fig. 5. It will be noted that in the pulse-cross pattern oi Fig. 6 there is a decided waver in the leit-hand edge oi the vertical white bar b which indicates a variation oi the edge of the line-synchronizing pulses and the initiation oi the line-retrace intervals. Since the leit-hand edge of the vertical grey bar lr is linear, the nonlinearity of the edge of the vertical white bar indicates a periodic phase shiit in the derivation of the 13,230-cycle line-synchronizing pulses from the 26,460-cycle oscillator oi the timer. It is iurther evident that the vertical white bar b-has a decided break in its leit-hand edge at the center thereoi. The depressed portions oi this break indicate that the equalizing pulses d are improperly delayed in phase with respect to the line-synchronizing b. The vertical synchronizing pluses e are advanced in phase with respect to the linesynchronizing pulses b as evidenced by the termination oi the gap I in the horizontal white bar e in advance oi the leit-hand edge oi the vertical white bar b. .The short duration of the gap I in the horizontal white bar e indicates that the duration t1 0! the broad pulses e is too long, a condition leading to improper line-frequency synchronization at the receiver. And, lastly, the pattern oi Fig. 6 indicates that the wave form oi the equalizing pulses d is improper in that the duration is oi these pulses is materially longer than one-half the duration t: oi the linesynchronizing pulses b. This condition also may contribute to improper synchronization at the receiver.

Fig. 7 is a circuit diagram oi a modified iorm oi field-synchronizing system which may, in certain instances, be used in place oi the delay circuit shown in the Fig.1 arrangement oi the wave iorm indicating system Is. This modiby the carrier-signal am-.

the antenna system system it i -connectedacrossthe varying with fication may be used where the transmitter and receiver are connected to'the same alternating current power-supply system or may be used at lieu oi synchronizing the indicatin systcm lliromthetimerlloithe transmitting apparatus. In this modification, a phase-shifting means or network comprising a condenser It and an adjustable resistor It is secondary winding Bl oi a transformer El, the primary l1 oi which comprises a supply circuit which is connected to an alternating current'power-supply main having a frequency equal to that of the field-synchronizing component of the television signal. A center tap on the winding 55 is grounded and the synchronizing circuit oi the field-scanning generator 23 is coupled between the junction oi the resistor 84 and the condenser 53 oi the phaseshiiting network and ground.

In considering the operation of this modified iorm oi field-synchronizing system, it will be evident that the alternating voltage developed between ground and the common terminal oi the condenser it and resistor it has substantially a constant amplitude and phase shiit with respect to the alternating voltageoi the powersupply mains, the magnitude oi the phase shiit the value of resistance oi resistor 54. when the wave form indicating system It ci the invention uses this modified form of fieldsynchronizing system ior maintaining the deflection fields in predetermined phase-displaced synchronism with reference to the field-synchronizing components, the operation oi the indicating system is otherwise essentially the same as in the arrangement oi Figs. 1 or 5 and will not be repeated.

From the above description oi the invention, it will be evident that a wave form indicating system embodying the invention has the advantages that it provides in a single visual pattern an indication oi the complete wave iorm oi a television signal and particularly of the portions thereoi which are essential to accurate synchronization between the transmitting and receiving apparatus. The pattern not only protides an indication of the individual durations oi the synchronizing-signal components and the durations of the line-retrace and field-retrace intervals, but additionally iurnishes an indication of the relative phase relationships between the several synchronizing-signal components. Such phase relationships and time durations can be accurately determined by reference to the vertical white lines which are produced by the output of harmonic generator '33 and are spaced across the pattern irom one side to the other.

Although the invention as above described has been utilized for producing a visual indication oi at least a portion of the wave form of a television signal, it will be understood that the in vention is applicable generally ior visually indicating any electrical phenomenon so long as an electrical signal of periodic wave worm representative oi the phenomenon is applied to the ray-control electrode of the cathode-ray tube included in the indicating arrangement to produce on the screen a visual trace indicative oi the phenomenon.

While there have been described what are at present considered to be the preferred embodiments oi this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, thereiore,

- fleeting the ray of components, means for periodically deflecting the ray of said tube in each of two directions normal toeach other, means for controlling said deflecting means to maintain said deflections in synchronism with the synchronizing-signal components of said applied signal, and means for maintaining a predetermined phase displacement between one of said deflections and a corresponding one of said synchronizing-signal components.

2. A system for visually indicating at least a portion of the wave form of a television signal comprising, a-cathode-ray tube having an input circuit adapted to have applied thereto a television signal to modulate the ray of said tube, said applied signal including synchronizingsignal components, means for periodically deflecting the ray of said tube in each of two directions normal to each other, means for controlling said deflecting means to maintain said deflections in synchronism with the synchronizing-signal components of said applied signal, and means for maintaining predetermined phase displacements between said ray deflections and said synchronizing-signal components.

3. A system for visually indicating at least a portion of the wave form of a television signal comprising, a cathode-ray tube having an input circuit adapted to have applied thereto a tele- I vision signal to modulate the ray of said tube, said applied signal including synchronizing-signal components, means for periodically deflecting the ray of said tube in each of two directions normal to each other, means for controlling said deflecting means to maintain said deflections in synchronism with the synchronizing-signal components of said applied signal, and means for delaying the phase of said ray deflections relative to corresponding ones of said synchronizing-signal components. v

4. A system for visually indicating at least a portion of the wave form of a television signal comprising, a cathode-ray tube having an input circuit adapted to have applied thereto a television signal to modulate the ray of said tube, said applied signal including synchronizing-signal components and being applied with such polarity to said input circuit that said synchronizingsignal components increase the beam current of said cathode-ray tube, means for periodically desaid tube in each of two directions normal to each other, means for controlling said deflecting means to maintain said deflections in synchronism with the synchronizing-signal components of said applied signal, and means for maintaining a predetermined phase displacement between one of said deflections and a corresponding one of said synchronizing-signal components.

5. A system for visually indicating at least a portion of the wave form of a television signal comprising, a cathode-ray tube having an input circuit adapted to'have applied thereto a television signal to modulate the ray of said tube, said applied signal including synchronizing-signal components, means for periodically deflecting the said applied signal ray of said tube in each of two directions normal to each other, means for controlling said deflect,- ing meansto maintain said deflections in synchronism with the synchronizing-signal components of said applied signal, and means for maintaining a predetermined phase displacement between one ofsaid deflections and a correspondof said one ray deflection.

6. A system for visually indicating at least a portion of the wave form of a television signal comprising, a cathode-ray tube having an input components, means for periodically deflecting the ray of said. tube in each of two directions normal to each other, means for controlling said deflecting means to maintain said deflections in synchronism with the synchronizing-signal components or said applied signal, means for maintaining a predetermined phase displacement between one of said deflections and a corresponding one of said synchronizing-signal components, and means for so adjusting the level in said input circuit of said applied signal that at least predetermined portions of said synchronizing-signal components are reproduced by said tube.

7. A system for visually indicating at least a portion of the wave form of a television signal comprising, a cathode-ray tube having input electrodes connected in an input circuit adapted to have applied thereto a television signal to modulate the rayof said tube, said applied signal including synchronizing-signal components, means for periodically deflecting the ray of said tube in each of two directions normal to each other means for controlling said deflecting means to maintain said deflections in synchronism with the synchronizing-signal components of said applied signal, means for maintaining a predetermined phase displacement between one of said deflections and a corresponding one of said synchronizing-signal components, and means for so biasing said input electrodes that at least predetermined portions of said synchronizing-signal components are reproduced by said tube.

8. A system portion of the wave form of comprising, a cathode-ray tube having an input circuit adapted to have applied thereto a television signal to modulate the ray of said tube,

including synchronizingsignal components, means for periodically deflecting the ray of said tube in each of two directions normal to each other, a signal delay circuit, and means including said delay circuit for controlling one of said deflecting means to maintain a corresponding one of said deflections in predetermined phase-displaced synchronism with a corresponding one of said synchronizing-signal components.

9. A system for visually indicating at least a portion of the wave form of a television signal comprising, a cathode-ray tube having an input circuit adapted to have applied thereto a tele vision signal to modulate the ray of said tube, said applied signal including synchronizing-signal components, means for periodically deflecting the ray of said tube in each of two directions normal to each other, two signal delay circuits, and means including said delay circuits for controlling said deflecting means to maintain said for visually indicating at least a I a television signalof said tube in each predetermined phase-displaced deflections in v synchronism withsaid synchronizing-signal components.

10. A system for nizing pulses, means for therayoisaidtubeina chronism with said line-frequency synchronizing pulses and periodically in a direction normal thereto in synchronism with said field-synchronizing pulses, a signal delay network having a phase delay of the period said line-synchronizing and means including said delay network for controlling said deflecting means to maintain between said line deflections and said line-synchronizing pulses a phase delay equal to said predetermlned portion of the period of said line-synchronizing pulsed.

11. A system for visually indicating at least a portion or the wave form of a television signal comprising, a cathode-ray tube having an input circuit adapted to have applied thereto a television signal to modulate the ray of said tube, said applied signal including synchronizing-signal components comprising line-synchronizing pulses, means for deriving synchronizing pulses displaced in phase with respect to said line-synchronizing pulses. means. for periodically deflecting the ray of said tube in each of two directions normal to each other to produce a series or lines and a series of fields, and means responsive to said derived synchronizing pulses for controlling said deflecting means to maintain said line deflections in phase-displaced synchronism with said line-synchronizing pulses.

12. A system for visually indicating at least a portion or the wave form of a television signal comprising, a cathode-ray tube having an input circuit adapted to have applied thereto "a television signal to modulate the ray of said tube,

said applied signal including snychronizing-signal components comprising field-synchronizing pulses, means for periodically deflecting the ray of said tube in each of two directions normal to each other to produce a series of flelds each consisting or a series of lines, an oscillator, means responsive to said field-synchronizing pulses for controlling the frequency of oscillations generated by said oscillator, and means responsive to said generated oscillations for controlling said defleeting means to maintain said series oi fields in predetermined phase-displaced synchronism with respect to said field-synchronizing pulses.

13. A system for visually indicating at least a portion of the wave form of a television signal comprising, a cathode-ray tube having an input circuit adapted to have applied thereto a television signal to modulate the ray of said tube, said applied signal including synchronizing-signal components comprising field-synchronizing pulses, means for periodically deflecting the ray of two directions normal to each other to produce a series of fields each consisting of a series of lines, an oscillator, means responsive to said field-synchronizing pulses for controlling the frequency of oscillations generated by said oscillator, means for controlling the wave form or said generated oscillations, and

portion of the comprising, a cathode-ray tube having an input tain said deflections means responsive to the wave tom of said generated oscillations for con said deflecting meanstomaintainsaidserieaoifleldsinpredetermined phase-displaced relation with respect to said field-synchronizing pulses.

14. A system for visually indica wave term or a television signll circuit adapted to have applied thereto a television signal to modulate the ray of said tube, said applied signal including synchronizing-signal components comprising field-synchronizing pulses, means for periodicall deflecting the ray of said tube in a first direction, means including a field-frequency oscillator for periodically deflecting the ray of said tube in a direction normal to said first direction. a multivibrator ior generating oscillations of substantially rec wave form, means responsive to said field-synchronizing pulses. tor sync said multivibrator at a predetermined point on hall-cycles 0! one polarity of said generated oscillations, and means for synchronizing said field-frequency oscillator at a predetermined point of the hallcycles of opposite polarity of said generated oscillations.

15. A system for visually indicating at least a portion of the wave iorm o! a television signal comprising, a cathode-ray tube having an input circuit adapted to have applied thereto a television signal to modulate the ray of said tube, said applied signal including line-synchronizing and field-synchronizing signal components, means for periodically deflecting the ray 0! said tube in a first direction in synchronism with said line-synchronizing component, means including a field-frequency oscillator for periodically deflecting the ray of said tube in a direction normal to said first direction, a supply circuit adapted to have applied thereto an alternating voltage the frequency 01 which is equal to that of said field-synchronizing component, and phase-shifting means coupled to said supply circuit for controlling said field-frequency oscillator to mainpredetermined phase-displaced synchronism with respect to said field-synchronizing component.

16. A system for visually indicating at least a portion of the wave form of a television signal comprising, a cathode-ray tube having an input circuit adapted to haveapplied thereto a television signal to modulate the ray of said tube, said applied signal including synchronizing-signal components, means for periodically deflecting the ray of said tube in each of two directions normal to each other, means for controlling said deflecting means to maintain said deflections in synchronism with the synchronizing-signal components of said applied signal, means for maintaining a predetermined phase displacement between one of said deflections and a corresponding one of said synchronizing-signal components, and means for additionally modulating the ray of said tube at a predetermined frequency related to said synchronizing-signal components to provide time-reference indicia on the screen of said cathode-ray tube.

17. A system for visually indicating at least a portion of the wave form 0! a television signal comprising, a cathode-ray tube having an input circuit adapted to have applied thereto a television signal to modulate the ray of said tube,

atleasta' in said second direction in of said tube trical phenomenon comprising,

2,284,219 normal to each other, means for controlling said deflecting means to maintain said deflections in synchronism witli the synchronizing-signal components of said applied signal, means for maintaining a predetermined phase displacement between one of said deflections and a corresponding one of said synchronizing-signal components, means for generating oscillations having a frequency' equal to a predetermined multiple of that of one of said synchronizing-signal components, and means for modulating the ray of said tube with said generated oscillations to provide timereierence indicia on the screen of said cathoderay tube.

18. A system for visually indicating an elec-- trical phenomenon comprising, a cathode-ray tube having a ray-control electrode adapted to have applied thereto an electrical signal representative of said phenomenon and to modulate the ray of said tube, means for deflecting the ray of said tube in one direction to produce on the screen of said tube a visual indication of said phenomenon, means for producing on, the screen of said tube visual timer-reference indicia from sentative of said phenomenon and to modulate the ray said tube, means for deflecting the ray of said tube in one direction tiallp constant velocity to produce determined comprising means for developing a periodic potential having a period equal'to a predetermined fraction of the time required for one deflection oi said my across the screen of said tube, and means responsive to said periodic poof said phenomenon, means for producing on the screen of said tube visual time-reference indicia potential for additionally modulating the ray of said tube.

21. A- system for visually indicating an eleca cathode-ray tube having a ray-control electrode adapted to values of said phenomenon may have applied thereto an electrical signal of pe riodic wave form representative of said phenomenon and to modulate the ray of said tube,

5 to produce on the screen of said tube a visual indication of said phenomenon, means for producing on the screen of said tube visual time-reference indicia from which the be determined comprising means for developing a periodic potential having a period equal to a predetermined fraction of the time requiredfor one deflection of said ray across the screen of said tube, and means responsive to said periodic potential for additionally modulating the ray of said tube.

22. A system for visually indicating an electrical phenomenon comprising, a cathode-ray tube having a ray-control electrode adapted to have applied thereto an electrical signal of periodic wave form representative of said phenomenon and to modulate the ray of said tube, means for periodically deflecting the ray of said tube in one direction to produce on the screen of said tube a visual indication ofsaid phenomenon, means for producing across the screen of said tube visual reference lines from which the values of said phenomenon may be determined comprising means for developing a periodic poperiod equal to a predetermined additionally modulating the ray of said tube.

23. A system for visually indicating an electrical phenomenon comprising, a cathode-ray tube having a ray-control electrode adapted to have applied thereto an electrical signal representative of said phenomenon and to modulate the ray of said tube, means for deflecting the ray of said tube in one direction to produce on the screen of said tube a visual indication of said phenomenon, mean for producing on the screen or said tube visual time reference indicia from fraction of the time required for one deflection means responsive to said periodic potential for additionally modulating the ray of said tube.

24. A system for visually indicating an electrical phenomenon comprising, a cathode-ray tube having a modulation-control electrode adapted to have applied thereto an electrical signal representative of said phenomenon and to modulate the ray of said tube, means for periodically deflecting the ray of said tube in two directions normal to each other to produce on said tube a visual indication of said phenomenon, means for producing across the screen of said tube visual reference lines from which the values of said phenomenon may be determined comprising means for deriving a peeriodic potential efiectively of pulse wave form and having a period equal to apredetermined fraction of the time required for one deflection of said ray across the screen of said tube, and means for ARTHUR V. LOUGHREN. 

